Sort beans and discard any rocks or damaged beans. Rinse.
Place beans, garlic, rosemary and water in a pot and bring to a boil. Turn the flame lower, cover with the lid ajar, and simmer stirring occasionally.
About halfway through cooking, stir in ½ teaspoon salt (about 30-40 minutes into cooking). If necessary, add more water as the beans cook so that they remain covered by water.
Cook beans until soft and creamy, about 1 to 1-½ hours. The time varies depending on the specific batch of beans. Check several different beans for doneness before turning off the stove; sometimes not all the beans are ready at once. Drain and remove rosemary branch.